This invention relates to a character recognition system and, more particularly, to a system employing a single-gap magnetic read head for reading magnetized characters embodied in the form of E-13B character font.
In single-gap magnetic character reading systems, a single analog input waveform is obtained by passing the characters to be sensed, normally located on a document, beneath a magnetic read head at least as wide as the height of the characters and having a single flux gap. The signal generated by the read head is a derivative waveform representing the rate of change of magnetic flux traversing the head as the characters are scanned. Since the distribution of ink, and thus flux, associated with each different character is unique, the waveform derived for each different character uniquely identifies that character.
To simplify the timing of the waveform analysis process, the characters are provided with stylized geometric features which impart anticipatable timing characteristics to the derived waveforms. Thus, in accordance with this scheme, for reader identification, each character of the E-13B font is divided into a predetermined number of vertical segments. The characters are designed such that the distribution of ink undergoes significant change only at the boundaries between segments. Hence, peak fluctuations in the derived waveform caused by these variations in ink distribution can occur within predetermined time zones or windows during the character scan.
Prior character recognition systems have incorporated circuits for determining the amplitude of each of the peaks of the waveform which uniquely represents the character read. These peak amplitudes are normalized and then correlated with the known peak characteristics of each of the E-13B characters to identify the character read. An example of this type of recognition system may be found in U.S. Pat. No. 3,851,309. Critical to this type of recognition system is the method of timing the generation of the windows for sampling the waveform to detect the occurrence of each of the peaks in the waveform. In actual practice, it has been found that the characters imprinted on a document may be distorted such that portions of the symbol of character within the symbol outline are not covered with magnetic ink. Such a distortion may occur due to imperfections of the printing device employed to imprint a character on a document. Also, the pigment of the magnetic ink used by the printing device may not have been uniformly dispersed throughout the character outline. Such poorly defined or misprinted characters produce voltage waveforms that may resemble the waveform of a character other than the character that was intended to be printed, thereby causing a misread. Other errors may be introduced by variation of the speed of the document past the read head thereby displacing the position of the peak from that found in the standard character. It has also been found that documents become splattered with ink particles during the printing process which particles cause corresponding spurious signals in the reading head. All of these situations have caused mis-read operations in those recognition systems which are based solely on the correlation of peak amplitudes with a character reference standard.
It is therefore an object of this invention to provide an improved character recognition system which overcomes the above mentioned problems found in the prior art.
It is a further object of this invention to provide a character recognition system which functions independently of the speed of the characters past the read head.
It is a further object of this invention to utilize the maximum amount of information found in the waveform generated by the character that is read.
It is another object of this invention to provide a character recognition system which minimizes the effect of variations in ink intensity found in the characters that are to be read.
It is a still further object of this invention to provide a character recognition system which utilizes a plurality of parameters of the waveforms in determining the character read.